Rank the following events on a scale from 0 (Impossible) to 1 (Certain).
Label each event: Impossible, less likely, equally likely (even chance), more likely, certain.
Give reasons why you gave each event its ranking.
(A) The next Monday will come after Sunday.
(B) It will snow in Mumbai in July.
(C) An elephant will walk through your classroom today.
(D) You will greet at least one friend at school tomorrow. [Page No. 159]
(A) Certain (probability = 1).
By the standard ordering of days of the week, Monday always follows Sunday.
This is true by definition, there is no uncertainty involved.
(B) Impossible (probability = 0).
Mumbai lies in a tropical coastal region. July is the peak monsoon month there, with temperatures far above freezing. Snow has never been recorded in Mumbai in any month.
Therefore, this is an impossible event.
(C) Less likely / Impossible (probability = 0, but not strictly 0).
In a normal school setting, classrooms are not accessible to elephants. While it is theoretically possible in an extremely unusual scenario (e.g., a circus parade, a rural school near a forest with wild elephants), for almost all students the probability is acceptable zero. We classify this as 'less likely' bordering on impossible.
(D) More likely / almost certain (probability close to 1).
Most students have friends at school and it is a daily habit to greet them. Unless one is absent from school or has no friends there (both unlikely), this event is nearly certain.
Caution
Students should remember that the probability of any event always lies between and , inclusive. A value greater than or a negative value indicates a mistake.
